A system for performing spectroscopy, including a first frequency comb source outputting first electromagnetic radiation comprising a first frequency comb centered at a first wavelength and having a first repetition rate; a second frequency comb source outputting a second electromagnetic radiation comprising a second frequency comb centered at a second wavelength and having a second repetition rate; a nonlinear device positioned to receive the first frequency comb and the second frequency comb, wherein the nonlinear device interacts the first frequency comb and the second frequency comb through sum frequency generation or difference frequency generation so as to generate an output electromagnetic radiation; and a detection system outputting a signal in response to detecting an interference of the output electromagnetic radiation with a third electromagnetic radiation, the signal comprising information used for determining a spectrum of at least the first frequency comb or the second frequency comb.